Blow-molded plastic containers are becoming more commonplace in packaging edible consumer goods such as peanut butter, pickles, applesauce and like food products. Traditionally, such products have been supplied in wide mouth glass jars which provide a relatively heavy, inflexible, sturdy container. Blow-molded plastic containers have the advantages that their light weight reduces transportation costs.
Plastic containers are continually being re-designed in an effort to reduce the amount of plastic required to make the container. While there can be a savings with respect to material cost, the reduction of plastic can decrease container rigidity and structural integrity. Thus, a problem with plastic containers is that many forces act on, and alter, the as-designed shape of the container, particularly its dome configuration, from the time it is blow-molded to the time it is placed on a shelf in a store.
In the packaging of food and beverage products, blow-molded plastic containers can be used in the so-called "hot-fill" process, i.e. filling the containers with a food or beverage product at an elevated temperature, sealing the containers, and then allowing the food or beverage to cool. Internal vacuum forces act on the container as a result of hot-fill processing. Hot-fillable plastic containers must provide sufficient flexure to compensate for the internal changes in pressure and temperature, while maintaining structural integrity and aesthetic appearance. The flexure is most commonly addressed with vacuum flex panels positioned under a label below the dome.
External forces are applied to sealed containers as they are packed, shipped and stored. Filled containers are packed in bulk in cardboard boxes, or plastic wrap, or both. A bottom row of packed, filled containers may support several upper tiers of filled containers, and potentially, several upper boxes of filled containers. Therefore, it is important that the container have a top loading capability which is sufficient to prevent distortion from the intended container shape.
Dome region ovalization is a common distortion associated with blow-molded plastic containers, especially if hot-filled. Some dome configurations are designed to have a horizontal cross-section which is substantially circular in shape. The forces resulting from hot-filling can change the intended horizontal cross-sectional shape, for example, from circular to oval, creating carton packing and label adhesion problems, among others.
Although various containers having a specific dome configuration may function satisfactorily for their intended purposes, there is a need for a blow-molded plastic container, particularly a blow-molded plastic wide mouth jar or narrow neck bottle, having an improved reinforced dome which resists ovalization distortion due to hot-filling, and resists compressive distortions due to top loading. A container having the dome should be capable of being made from a minimum of plastic to afford efficient manufacture.